generatesDownloadContent

The default implementation returns false. Subclasses are
encouraged to return true here if they know that they are
generating download content that requires temporary caching on the
client side, typically via the response OutputStream.

The first step will be preparing the request: In the JSP case,
this would mean setting model objects as request attributes.
The second step will be the actual rendering of the view,
for example including the JSP via a RequestDispatcher.

mergePdfDocument

Subclasses must implement this method to merge the PDF form
with the given model data.

This is where you are able to set values on the AcroForm.
An example of what can be done at this level is:

// get the form from the document
AcroFields form = stamper.getAcroFields();
// set some values on the form
form.setField("field1", "value1");
form.setField("field2", "Vvlue2");
// set the disposition and filename
response.setHeader("Content-disposition", "attachment; FILENAME=someName.pdf");

Note that the passed-in HTTP response is just supposed to be used
for setting cookies or other HTTP headers. The built PDF document itself
will automatically get written to the response after this method returns.

Parameters:

model - the model Map

stamper - the PdfStamper instance that will contain the AcroFields.
You may also customize this PdfStamper instance according to your needs,
e.g. setting the "formFlattening" property.